TW201605195A - Method and apparatus for table aging in a network switch - Google Patents

Abstract

Embodiments of the present invention relate to a centralized table aging module that efficiently and flexibly utilizes an embedded memory resource, and that enables and facilitates separate network controllers. The centralized table aging module performs aging of tables in parallel using the embedded memory resource. The table aging module performs an aging marking process and an age refreshing process. The memory resource includes age mark memory and age mask memory. Age marking is applied to the age mark memory. The age mask memory provides per-entry control granularity regarding the aging of table entries.

Description

Table aging method and device in network switch

The present invention relates to table aging in high speed network switches. More specifically, the present invention relates to methods and apparatus for table aging in network switches.

The prior art network switch implements table aging. Specifically, the lookup is done at a table during the packet processing phase. The matching entries in the table are marked as hits. The entry hit information for all table entries is stored in the memory. A periodic hardware or software program monitors entry hit information. An action can be performed if the table entry has not been hit for a while. For example, aging of MAC addresses is used to evict and update forwarding table entries. In some other cases, this mechanism can be used for network debugging.

Prior art network switches allocate a fixed set of memory used to age a fixed set of tables. In modern system-on-a-chip (SOC) designs, the area and power budget of embedded memory typically dominates the total wafer budget. As a result, efficient and flexible use of limited memory resources is critical.

Software Definition Networking (SDN) is already a disruptive innovation for the industry And appeared. It promotes the separation of control planes and high-speed data planes for network devices. Traditionally, network control, such as flow management, routing updates, and table aging, is done in specialized hardware switch chips. However, in the new SDN era, these complications have been moved into separate controllers. Such changes require a new and different approach to the data plane, and most particularly the architecture and implementation of the network switch chip.

Embodiments of the present invention relate to a centralized table aging module that efficiently and flexibly utilizes embedded memory resources, and the centralized table aging module implements and facilitates separate network controllers . The centralized table aging module uses embedded memory resources to perform aging of the tables in parallel. The table aging module performs an age tagging process and an age refresher. Memory resources include age-labeled memory and age-shielded memory. Apply age markers to age-labeled memory. The age mask memory provides subtle control of each item regarding the aging of the table entries.

In one aspect, a network switch is provided. The network switch includes at least one core, the at least one core including a plurality of processing units. The network switch also includes on-wafer memory on which the memory stores a plurality of search tables. A plurality of processing units communicate with memory on the wafer to perform a table search. The network switch also includes a table aging module, and the table aging module includes its own embedded memory. The table aging module is capable of aging any of the plurality of search tables. In some embodiments, once a search table is hit, the table aging module receives the table ID and the hit address from the corresponding search request.

In some embodiments, the table aging module performs an age tagging process and Age refresh program. The age tagging program sets the age memory bit to be flagged (eg, 1) whenever a corresponding search table hit occurs. The age refresh program checks all age memory bits corresponding to the search table. The check occurs periodically based on the configured cycle time or specifically triggered by the software. When the age memory bit is unmarked (eg, 0), the software is notified that the corresponding table entry is out of date, and when the age memory bit is marked (eg, 1), the age memory bit is reset to unmarked (eg, , 0), in preparation for the next round of age markers and age refresh.

In some embodiments, the network also includes an aging configuration set used by the table aging module. The aging configuration set includes configuration, age profiles, and a central aging memory pool.

In some embodiments, each of the plurality of search tables is in an aging configuration in the aging configuration and includes an aging enable bit and an indicator that points to one of the age profiles.

In some embodiments, each age profile in the age profile specifies a refresh period for the search table and specifies an aging memory allocation in the central aging memory pool. The central aging memory pool is embedded. Alternatively, the central aging memory pool is part of the memory on the wafer.

In some embodiments, the central aging memory pool includes age tag memory and age mask memory. In some embodiments, each of the age tag memory and the age mask memory comprises a plurality of physical memory tiles, wherein the memory of the central aging memory pool is grouped into blocks. Mark ages for age-coded memory applications. The age mask memory provides subtle control of each item, where the corresponding table entry is not specified when the mask bit is set to 0. With the aging program.

In another aspect, a table aging module in a network switch is provided. The table aging module includes an aging memory block. Aging memory blocks typically include age-labeled memory and age-shielded memory.

The table aging module also includes an age tagging program. The age tagging program typically includes an input queue for caching the age tag input to the aging memory block for the table hit.

The table aging module also includes an age refresh program. The age refresh program typically includes a bitwise OR operation of the read age mark data in the age tag memory and the inverse value of the mask bit in the age mask memory.

In some embodiments, the table aging module also includes an age interrupt queue. When the result of the operation is not all ones, the result and the memory block address and the column address for the aging memory column are pushed into the age interrupt queue, which corresponds to the set of search table entries.

In some embodiments, the table aging module also includes a refresh state machine for controlling the age refresh program.

In yet another aspect, a method of a network switch is provided. The method includes processing a plurality of table search requests in parallel. The method also includes generating information for processing by the table aging module when the table hits. The method also includes the table aging module using a central aging memory pool to coexist the aging of the execution table. The table aging module uses the generated information to perform aging of the table.

In some embodiments, the aging of the table includes two individual programs, including an age tag program and an age refresh program. In some embodiments, the age refresh procedure can be suspended.

In some embodiments, the method also includes, prior to processing the plurality of table search requests in parallel, programmatically assigning the first subset of the blocks as age tag memory, and programmatically assigning the second subset of blocks to The age tag memory and the table aging module can be configured programmatically.

100‧‧‧Network switch

105‧‧‧ core

110‧‧‧Traffic Manager

115‧‧‧Processing unit

120‧‧‧Processing unit

125‧‧‧ Memory on the wafer

130‧‧‧ table aging module

200‧‧‧Aging configuration set

205‧‧‧Configuration

210‧‧‧ age profile

215‧‧‧Central aging memory pool

300‧‧‧Central aging memory pool

305‧‧‧ age-labeled memory

310‧‧‧ age-shielded memory

400‧‧‧ table aging module

405‧‧‧ age-labeled memory

410‧‧‧ age screened memory

415‧‧‧Input queue

420‧‧‧Refresh state machine

425‧‧‧ age interruption queue

500‧‧‧ method

505-515‧‧‧Steps

The foregoing description of the preferred embodiments of the invention, The drawings are not necessarily to scale, the

The first figure illustrates an exemplary aspect of a network switch in accordance with an embodiment of the present invention.

The second figure illustrates an aging configuration set in accordance with an embodiment of the present invention.

The third figure illustrates an exemplary central aging memory pool in accordance with an embodiment of the present invention.

The fourth figure illustrates a block diagram of a table aging module in accordance with an embodiment of the present invention.

The fifth figure illustrates a method of aging in accordance with an embodiment of the present invention.

In the following description, numerous details are set forth for purposes of illustration. However, one skilled in the art will recognize that the invention may be practiced without these specific details. Therefore, the present invention is not intended to be limited to the embodiments shown, but the scope of the inventions

Embodiments of the present invention relate to a centralized table aging module that efficiently and flexibly utilizes embedded memory resources and implements and facilitates separate network controllers. The centralized table aging module uses embedded memory resources to perform aging of the tables in parallel. The table aging module performs an age tagging process and an age refresher. Memory resources include age-labeled memory and age-shielded memory. Apply age markers to age-labeled memory. The age mask memory provides subtle control of each item regarding the aging of the table entries.

The first figure illustrates an exemplary concept of a network switch 100 in accordance with an embodiment of the present invention. Network switch 100 includes one or more cores 105 and traffic manager 110. Each core 105 typically includes multiple pipeline stages. The plurality of pipeline stages includes a plurality of packet processing units 115 and at least one packet modifier 120. All of the processing units 115, 120 in one or more of the cores 105 communicate with the on-chip memory 125 to perform a table search. The on-chip memory 125 can store one or more search tables. The search table is age-enabled or age-deactivated. Each of the plurality of packet processing units 115 is capable of accessing one or more search tables.

The on-wafer memory 125 is coupled to the surface aging module 130. The table aging module 130 includes its own embedded memory. Embedded memory typically operates behind the on-wafer memory 125 for table search. Embedded memory can be used to age any search table in the table search memory pool 125. Generally, once a search table is hit, the aging module 130 of the first figure receives the table ID (Table ID) and the hit address from the corresponding search request.

The table aging module 130 executes at least two individual programs, including an ageing program and an age refresh program. For configuration as For those search tables that are enabled for aging, there are memory bits corresponding to each table entry in the embedded memory of the table aging module 130. The age tagging program sets the age memory bit to 1 whenever a corresponding search table hit occurs. The age refresh program checks all age memory bits corresponding to the search table based on the configured cycle time periodically (ie, the automatic aging mode) or specifically triggered by the software (ie, the trigger mode). If the age memory bit is 0, indicating that the corresponding table entry has not been hit since the previous aging refresh procedure, the software is notified that the corresponding table entry is out of date. If the age memory bit is 1, indicating that the corresponding table entry is active, the age memory bit is reset to 0 in preparation for the next round of age markers and age refresh.

There are typically many search tables in a feature-rich network switch, such as network switch 100. For example, there may be more than 160 search tables for the entire SOC wafer of network switch 100. Exemplary search tables include, but are not limited to, routing tables, access control lists (ACLs), flow meters, and the like. Direct aging of 160 or more search tables may be too much for a single processing of the SOC wafer and has less utility.

The second figure illustrates an aging configuration set 200 in accordance with an embodiment of the present invention. In some embodiments, the aging configuration set 200 is used by the table aging module 130 of the first figure. The aging configuration set 200 includes a configuration 205, an age profile 210, and a central aging memory pool 215.

In some embodiments, 64 age profiles 210 are provided for more than 160 search tables. However, more or less age profiles can be provided. Each of the search tables in the aging configuration 205 in the search table includes an aging enable bit (ie, age_en ) and an indicator pointing to one of the 64 age profiles 210 (ie, cfg_id ) . Age_en indicates whether the search table is aging enabled.

Each age profile 210 specifies a refresh period (ie, refr_period ) for the search table. The refresh period advantageously allows for different aging subtleties for flexibility in higher level systems. For example, a MAC table entry can be aged out after a few minutes of inactivity. As another example, the flow meter entry can be declared inactive after a few seconds. The age profile also specifies the aging memory allocation in the central aging memory pool 215 (ie, mem_row_offset , mem_row_inc ).

In some embodiments, the table aging module 130 of the first figure uses a centralized public memory pool. The aging memory pool 215 of the second figure is part of a centralized common memory pool. In some embodiments, the centralized public memory pool is embedded. Alternatively, the centralized common memory pool is part of the on-wafer memory 125 of the first figure.

In some embodiments, each table search request specifies whether a particular search should participate in the aging procedure, even if the corresponding search table is aging enabled. An example of this flexibility is the aging of the MAC table. Usually, there is only one table for MAC address lookup. Source MAC address lookups may want to participate in the aging process. However, the destination MAC address lookup may not want to participate in the aging procedure because the destination may have been removed from the current destination and the network switch is not aware of this.

The third figure illustrates an exemplary central aging memory pool 300 in accordance with an embodiment of the present invention. In some embodiments, the central aging memory pool 215 of the second map is similarly configured as the central aging memory pool 300. Central aging The memory pool 300 includes an age tag memory 305 and an age mask memory 310, each of which contains a plurality of physical memory blocks. In some embodiments, the memory of memory pool 300 is grouped into blocks. Blocks usually contain the same amount of memory. In some embodiments, each block is 64 bits wide and 2048 entries deep. As shown in the third figure, eight memory blocks are used to construct each of the age tag memory 305 and the age mask memory 310. However, each of the age tag memory 305 and the age mask memory 310 can be constructed with more or fewer memory blocks. The number of memory blocks for age tag memory 305 may be the same or different than the number of memory blocks used for age mask memory 310.

Age markers are applied to age-labeled memory 305 as described above. The age mask memory 310 provides fine control of each item. If the mask bit is set to 0, the corresponding table entry does not participate in the aging procedure. Each item controls the subtlety that provides many benefits. For example, the system wants to remove any obsolete entries in the routing table. However, there may be statically configured routing entries that should never be evicted.

The fourth diagram illustrates a block diagram of a table aging module 400 in accordance with an embodiment of the present invention. In some embodiments, the table aging module 130 of the first map is similarly configured as the aging module 400. The table aging module 400 allows table aging to be processed in parallel.

During the age tagging process, the age tag input to the aging memory block 405, 410 for the table hit is cached in the input queue 415, which may be a FIFO buffer, in the case of an aging memory excess. The software can be configured with an aging program to perfectly match the bandwidth of the age tag memory 405, which means that only a few tables will be aged. Alternatively, the software can configure an aging program to configure many tables to be aged. However, it is possible that not all table hits will be flagged, where the tags will become probabilistic. The age tag input for each table hit includes the table ID (ie, tbl_age ) and the table hit address. The table hit address is used to map exactly to a bit in a column of the corresponding age tag memory 405.

During the age refresh procedure, the read age mark data in age tag memory 405 and the inverse value bitwise OR (OR) value of the mask bit in age mask memory 410. If the result is all ones, then each entry in the entry has been hit during a previous refresh. However, if the result is not all ones, then there are one or more entries that have not hit during the previous refresh event. The age tag memory block address and column address and the data of the fetch value are pushed into the age interrupt queue 425, such as the FIFO buffer. The interrupt is then sent to the CPU, such as an external system CPU, for purposes of expulsion, network debugging purposes, and/or other purposes.

Refresh state machine 420 typically controls the age refresh program. Table 1 lists the configuration of the refresh state machine 420.

The mode of the aging unit (ie, the automatic aging mode or the trigger mode) is specified by the mode field. The unit_time field defines the number of clock cycles on which the aging event is based.

If the aging unit is in the automatic aging mode, the age refresh program periodically checks all memory locations corresponding to the search table based on the configured cycle time.

If the aging unit is in the trigger mode, the trig_cfg_bmp field indicates which of the 64 age profiles will perform the age refresh procedure when the system CPU writes.

Typically, the hardware aging program runs multiple orders of magnitude faster than the software in the CPU, and the age interrupt queue 425 may easily overflow. Based on the en_pause field, the refresh procedure can be suspended once the age interrupt 425 occupancy level exceeds a configured threshold as set by the fifo_thd field. The ageing program typically pauses until the CPU consumes an age interrupt 425 column below the configured threshold.

Due to limited memory hardware or processing speed, not all table hits can be flagged in an aging configuration, which can cause false aging alarms. However, due to the nature of network traffic, most active streams will have more than one packet passing through the switch. So even if a packet misses the age mark Preface, it is unlikely that all packets will miss the age tagging process, especially if the aging refresh cycle is reasonably long enough, this is the case for actual use cases. In addition, this hardware architecture enables software to implement different table aging mechanisms in higher level applications, such as aging with an age counter that is more than one bit wide.

The fifth figure illustrates a method 500 of aging in accordance with an embodiment of the present invention. Method 500 is typically performed by network switch 100 of the first figure. As discussed above, network switch 100 includes on-wafer memory 125. A plurality of packet processing units 115 communicate with the on-chip memory 125 to perform a table search.

At step 505, a plurality of table search requests are processed in parallel.

At step 510, at the time of the table hit, information is generated for processing by the table aging module.

At step 515, the table aging module uses the central memory pool to perform aging of the tables in parallel. Table aging modules typically use the information generated to perform aging of the table. As discussed above, the aging of the table includes two individual programs, including an age tag program and an age refresh program. The central aging memory pool includes age-coded memory and age-shielded memory.

The age tagging program includes an input queue for caching the age tag input for the aging memory block for the table hit, and the age refresh program includes the read age tag data in the age tag memory and the mask in the age mask memory. A bitwise OR operation of the inverse of a bit. If the result is all 1, each entry in the entry has been hit during the previous refresh or needs to be saved. However, if the result is not all ones, then there are one or more entries that have not hit during the previous refresh event. The memory block address and column address for those routing entries and the extracted data are pushed into the age interrupt queue. The interrupt is then sent to the CPU, such as an external system CPU, for purposes of expulsion, network debugging purposes, and/or other purposes. In some embodiments, the age refresh program can be suspended to prevent overflow of the age interrupt queue.

In some embodiments, method 500 also includes, prior to processing the plurality of table search requests in parallel, the first subset of the blocks can be programmatically assigned as age tag memory, and the second child of the block can be programmatically assigned The collection is used as an age tag memory and the table aging module can be configured programmatically. Unlike prior art networking switches that use dedicated memory for table aging, network switch 100 uses a centralized table aging module that efficiently and flexibly uses embedded memory resources for Table aging.

One of ordinary skill in the art will recognize that other uses and advantages exist. While the invention has been described with respect to the specific embodiments, the embodiments Therefore, those of ordinary skill in the art will understand that the invention is not limited by the details of the foregoing examples.

400‧‧‧ table aging module

405‧‧‧ age-labeled memory

410‧‧‧ age screened memory

415‧‧‧Input queue

420‧‧‧Refresh state machine

425‧‧‧ age interruption queue

Claims (25)

A network switch comprising: at least one core, the at least one core comprising a plurality of processing units; a memory on the wafer, the on-chip memory storing a plurality of search tables, wherein the plurality of processing units and the Memory communication on the chip to perform a table search; and a table aging module including its own embedded memory, wherein the table aging module ages any of the plurality of search tables . The network switch of claim 1, wherein the table aging module receives a table ID (Table ID) and a hit address from a corresponding search request once a search table is hit. The network switch according to claim 1, wherein the table aging module executes an age marking program and an age refreshing program. The network switch of claim 3, wherein the age tagging program sets an age memory bit to be marked each time a corresponding search table hit occurs. The network switch of claim 3, wherein the age refresh program checks all age memory bits corresponding to the search table. The network switch of claim 5, wherein the checking occurs periodically based on a configuration cycle time or is specifically triggered by the software. The network switch according to claim 5, wherein when the age memory bit is unmarked, notifying the software that a corresponding table entry is out of date, and when the age memory bit is marked, The age memory bits are reset to unmarked to prepare for the next round of age markers and age refresh. The network switch of claim 1, further comprising an aging configuration set, wherein the aging configuration set is used by the table aging module, wherein the aging configuration set includes a configuration, an age profile, and a Central aging memory pool. The network switch of claim 8, wherein each of the plurality of search tables is in an aging configuration in the aging configuration, and includes an aging enable bit and a pointing location An indicator of an age profile in the age profile. The network switch of claim 8, wherein each of the age profiles defines a refresh period of one of the search tables, and specifies one of the central aging memory pools to be aged. Memory allocation. The network switch of claim 8, wherein the central aging memory pool is embedded. The network switch of claim 9, wherein the central aging memory pool is part of the memory on the wafer. The network switch of claim 8, wherein the central aging memory pool comprises age tag memory and age mask memory. The network switch of claim 13, wherein each of the age tag memory and the age mask memory comprises a plurality of physical memory blocks, wherein the central aging memory pool The memory is composed of groups. The network switch of claim 13, wherein the age tag is applied to the age tag memory. The network switch of claim 13, wherein the age masking memory provides per-entry control nuance, wherein when a masking bit is set to 0, a corresponding table entry does not participate in an aging program. A table aging module in a network switch, the table aging module comprising: an aging memory block, the aging memory block comprising an age tag memory and an age mask memory; an age tagging program, The age tagging program includes an input queue for one of the age tag inputs of the aging memory block for buffering table hits; and an age refresh program including a readout in the age tag memory The age marker data is one-by-one or (OR) computed with one of the inverse values of a mask bit in the age masked memory. The table aging module according to claim 17, further comprising an age interrupt queue. The table aging module according to claim 18, wherein when the result of the operation is not all 1, the result and the memory block address and A column address of an aging memory column is pushed into the age interrupt queue, the aging memory column corresponding to a set of search table entries. The table aging module of claim 17, further comprising a refresh state machine for controlling the age refresh program. A method of a network switch, the method comprising: processing a plurality of table search requests in parallel; generating information for processing by a table aging module when a table is hit; and using a central memory by the table aging module The body pool performs the aging of the table in parallel. The method of claim 21, wherein the table aging module uses the generated information to perform the aging of the table. The method of claim 22, wherein the aging of the table comprises two individual programs, the two individual programs comprising an age marking program and an age refresh program. The method of claim 23, further comprising suspending the age refresh procedure. The method of claim 23, further comprising: before processing the plurality of table search requests in parallel: programmatically assigning a first subset of the blocks as age tag memory; programmatically assigning A second subset of the blocks is used as age masking memory; and the table aging module is programmable.